Port and starboard

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View of the port side of the superliner RMS Queen Mary 2
View of the starboard side of the Freedom of the Seas cruise ship

Port and starboard are nautical terms which refer to the left and right sides, respectively, of a ship as perceived by a person on board facing the bow (front of the ship). In lay terms, when observing the bow from the bridge of a watercraft, port refers to the left side of the ship and starboard refers to the right.

At night, the port side of a vessel is indicated with a red navigation light and the starboard side with a green one. These terms can also be applied to aircraft, particularly to airships in naval use, and eventually for all forms of heavier-than-air aircraft, particularly for the waterborne seaplane, existing in both floatplane and especially for flying boats of both civilian and military types, with aircraft of all types even adopting similar navigation lights to those of boats and ships.

The starboard side of most naval vessels the world over is designated the "senior" side. The officers' gangway or sea ladder is shipped on this side and this side of the quarterdeck is reserved for the captain. The flag or pennant of the ship's captain or senior officer in command is generally hoisted on the starboard yard.

view of RMS Titanic's port side



Man sailing a corbita (a small coastal vessel with two masts). Marble relief, ca. 256 AD, probably made in Africa Proconsularis (Tunisia). Found at Carthage.

The origin of the term starboard comes from early boating practices. Before ships had rudders on their centrelines, they were steered by use of a specialized steering oar, which was held by an oarsman located in the stern of the ship and, due to the prevalence of right-handed sailors, on the right-hand side of it. The word starboard comes from Old English steorbord, literally meaning the side on which the ship is steered, cognate with the Old Norse words stýri meaning "rudder" (from the verb stýra, "to steer" or "to govern") and borð meaning etymologically "board", then the "side of a ship".


An early version of "port" is larboard, which itself derives from Middle-English ladebord. In Old English the word was bæcbord, of which cognates are used in other European languages, for example as the German backbord and the French term (derived from Dutch) bâbord. The origin of lade has not been determined but some would connect it with the verb lade (to load), referring to the side on which cargo was loaded.[1] The term larboard, when shouted in the wind, was presumably too easy to confuse with starboard[2] and so the word port came to replace it. Port is derived from the practice of sailors mooring ships on the left side at ports in order to prevent the steering oar from being crushed.

Larboard continued to be used well into the 1850s by whalers, despite being long superseded by "port" in the merchant vessel service at the time. "Port" was not officially adopted by the Royal Navy until 1844 (Ray Parkin, H. M. Bark Endeavour). Robert FitzRoy, captain of Darwin's HMS Beagle, is said to have taught his crew to use the term port instead of larboard, thus propelling the use of the word into the Naval Services vocabulary.


Before modern standardization, quartermasters were advised to follow the rotation of the bottom of the wheel. Thus, when obeying a "hard a-starboard" command, the QM would turn the bottom of the wheel to the right, or starboard. This applied the left rudder and the ship turned to its left, or to port. Steering with the bottom of the wheel was apparently an approved way to learn helming more than a century ago.

The nautical reason for a "hard a-starboard" command to turn left seems related to the tiller and not the rudder. A tiller is pushed to the right, or starboard, to apply left rudder and turn the vessel to the left.

Right-of-way for other vessels[edit]

Vessels at sea do not actually have any "right-of-way"—they may be, correctly, in the position of being the "stand-on vessel" or the "give-way" vessel. Therefore, at no time should any vessel actually navigate its way into a collision, and the regulations are clear that no one in command of a vessel may assume a "right-of-way" up to a point of collision.

Right of way at sea - Diagram showing the (expected) behavior of ships that are on a collision course

Consider two ships on courses that intersect. The ordinary rule is that the ship on the left must 'give way'. The stand-on vessel (right) sees the green light on the starboard (right) side of the ship on the left i.e., 'give-way vessel' (left). The 'give-way vessel' (left) sees the red light on the port side of the 'stand-on vessel' (right). If the courses are intersecting, the helmsman usually gives way to a red light by going around the stern of the stand-on vessel.

There are other rules governing which is a stand-on vessel, such as the wind based rules for sailing vessels, powered ships giving way to sailing ships, and all other ships giving way to powered vessels that are constrained by their draft or restricted in their ability to maneuver. Therefore the green light does not mean an unqualified go, but rather it means proceed with caution subject to other rules applying. The earliest railway signals went red/green/white (as per the stern light) for stop/caution/go following this naval practice and were only later changed to the more familiar red/yellow/green.

The very simple application of red light and green light is to remember the rhyme "If to starboard red appear, 'tis your duty to keep clear" meaning that if the helmsman sees a red light on his starboard side he is the give-way vessel. The sailing rule that dictates that a sailing vessel on starboard tack is the stand-on vessel is as old as any other regulation. Likewise, if on the same tack, a sailing vessel that is upwind of another is the give-way vessel. When ships still had rudders on the starboard of the vessel, the rudder can lift farther out of the water on a starboard tack due to the boat being healed over in higher winds. This caused the boat on a starboard tack to have less control than a vessel on port tack and therefore the port tack vessel must give way.


Approaching motor vessel with lights indicating starboard (green) and port (red) sides, a length of more than 50 metres, with motor propulsion and in waters where COLREG apply.
Views of motor vessels with port and starboard lights (Seaman's Pocket-Book, 1943)

After dark, red and green sidelights are used on vessels to indicate the port and starboard sides, respectively. The red (port) and green (starboard) sidelights are each lit from right ahead to 22.5 degrees abaft the beam on its corresponding side. In international waters, the lighting of vessel is standardized in §23 Part C COLREG.

Mnemonic devices[edit]

Regarding directional navigation lights, "red, right, returning" is a common mnemonic used by sailors to remember which side is which and direction of movement when observing other craft on the water at night. For example, if the sailor sees lights on the horizon with a red light on the observer's right side (and green on the left), the observer knows the craft is moving toward him, not away. The mnemonic refers to: red (running or navigation light), right (side), returning (from sea, toward you).

There are a number of mnemonics that have been used day or night to remember which sides are port and starboard:


A port buoy is a lateral buoy used to guide vessels through channels or close to shallow water. The port buoy is one that a vessel must leave to port when passing upstream. If in International Association of Lighthouse Authorities area A, the port buoys are red. If in IALA area B (Japan, the Americas, South Korea, and the Philippines) then the "handedness" of buoyage is reversed, and a vessel leaves black or green buoys to port.

Mnemonic devices for buoys in IALA area B:

Use in aviation[edit]

As aerodynamically controllable, powered aircraft of both lighter-than-air (starting with Henri Giffard's pioneering airship of 1852) and heavier-than-air (Wright Flyer I of 1903) forms evolved, the nautical practice of using "port" and "starboard" for aircraft began to be considered for aeronautical use - following the first successful seaplane flight in late March of 1910, and the adoption of airships by naval forces, the term began to become mainstream, with their full adoption occurring with the success of flying boat waterborne aircraft early in the 20th century.[3]

See also[edit]


  1. ^ Oxford English Dictionary, etymology of larboard
  2. ^ Norie, John William; Hobbs, J. S. (1847) [1840]. Sailing directions for the Bay of Biscay, including the coasts of France and Spain, from Ushant to Cape Finisterre ("A new ed., rev. and considerably improved" ed.). C. Wilson. p. 1. OCLC 41208722. Retrieved 7 February 2010. An order, recently issued by the Lords Commissioners of the Admiralty, states, that in order to prevent mistakes, which frequently occur from the similarity of the words starboard and larboard, in future, the word port is to be substituted for larboard, in all Her Majesty’s ships or vessels. 
  3. ^ "AVIATION/NAUTICAL INFORMATION". http://www.nrotc.web.arizona.edu/. University of Arizona NROTC. Retrieved December 21, 2013. 

Further reading[edit]

External links[edit]